1) Field of the Invention
This invention relates to the formulation of a cleaning agent which is capable of cleaning wellbore and water-wet the surface.
2) Background Information
Various fluids, including oil based mud (OBM), synthetic oil based mud (SBM) and/or water based mud (WBM), were applied during the wellbore drilling process for the exploration and/or production of fossil fuel. During drilling, mud is circulated continuously and leaves the wellbore surface and other surfaces contaminated. Effective drilling mud removal is a necessary for both cementing success and completion operations. Before cementing, the casing and formation need to be water-wet so that cement can bond with both casing and formation. Before completion of a well, it is necessary to displace the mud and water-wet the casing, tubular so that clean fluid, typically clear solids-free brine, can be placed into the well. Conventional cleaning methods use fresh water or seawater treated with cleaning agents to displace the mud and water-wet the surfaces. This low-density treating fluid creates a negative differential pressure between the working fluid and the formation, which frequently require unacceptable pump pressure. Weighed spacers or cleaning fluids can overcome the differential pressure problem. A weighted spacer generally composes of a viscosifier, weighting material, and cleaning agent. Xanthan gum and other water-soluble polysaccharides are frequently used as viscosifier. Barite, calcium carbonate and others solid material are frequently used as weighting material. Heavy weight brine can be used as weighting material as well. However, the weighted cleaning fluids generally have limitation on the cleaning efficiency.
Accordingly, there is a demand for highly effective cleaning agents that can be applied in displacement spacers to remove mud residue and leave the surface clean and water-wet.